The present invention also relates to a golf club set.
State of the prior art "Iron" type golf clubs have a shaft to which a head with a generally four-sided shape is fixed, having a striking face forming a certain angle, or "face angle" ("loft") with a plane containing the shaft axis, and parallel to the lower edge of the striking face. Moreover, said lower edge forms a certain angle, or "lie", with the shaft axis.
The face angle is chosen to be as large as one desires in order to manufacture a club which produces high and short trajectories. In this case, the shaft is relatively short and the mass of the head is chosen to be relatively high. On the contrary, with a small face angle, a long shaft and a light mass, the kinetic energy of impact on the ball produces a long and low trajectory. For decades thinking on this subject has been locked into this logic. This is why the construction of modern "Irons" has been codified for the last half-century in such a way that the player must choose between playing a ball high but short, or on the other hand playing a ball long but low.
In fact, until now, the complete series of commercially-available irons, which are usually numbered from 1 Iron to 9 Iron, "Pitching Wedge" (or 10 Iron) and "Sand-Wedge" are all designed in such a way that an increasing face angle ("loft") corresponds to an increasing surface, volume and weight of the club head, and a decreasing length of shaft.
Thus the 1 Iron will have the longest shaft of the irons in the bag (approx. 1.05 m), and the smallest face angle, about 18.degree., i.e. a virtually vertical striking face; it will produce the longest (200 m) and lowest (12 m) trajectories, the ball running on furthest after its flight. At the other end of the scale, a "Sand-Wedge" Iron will have a significantly shorter shaft (approx. 0.89 m), a heavier head, with a larger striking face which is very inclined (about 56.degree.) and will produce the shortest (80 m) and highest (25 m) trajectories, the ball stopping almost immediately after hitting the ground.
The shaft length plays an important role. The longer the shaft the greater the muscle power required to give the club a specific angular velocity when the ball is struck. But for a given angular velocity, the velocity of the head increases proportionally to the length of the shaft. The kinetic energy imparted to the ball, which is proportional to the square of the velocity at the moment of impact, is therefore, for a given angular velocity, proportional to the square of the shaft length.
These considerations and others, connected with the experience and physical stamina of players, has led to the classic set of "Irons" mentioned above being preferred.
It should be noted that the lengths in question are those envisaged for a male of average height, i.e. between 1.7 m and 1.8 m.
For a woman of average height, this being between about 1.55 m and 1.65 m, the length of the "Iron" of the same number is reduced by one inch, i.e. about 2.5 cm.
The lie angle is such that the lower edge of the striking face rests horizontally on the ground when the club rests on the ground while being gripped in a normal manner by a person being of the height for which the club was designed.
As the shaft length varies according to the height of the persons for whom each club is intended, the lie angle can be substantially independent of the person's height.
With state-of-the-art Irons, the player who is preparing to play the ball knows that he stands along the vertical axis of a conical space, the base of which is adjacent to the ground, and that the ball is not able to go beyond this conical space. Either the ball is played high and will remain relatively close to the axis or the ball is played long and the maximum altitude of its trajectory is reduced. Moreover, this appears to be logical.
Now, in numerous situations in play, golfers may wish to play a ball both long and high with the precision of an "iron", for example to clear a high and fairly distant obstacle without going too far past it, or to get out of moderately thick rough with a shot of power and distance, or to get out of a fairway bunker (sand trap) which has an elevated rim with a long shot, or to hit the green on certain "Par 3" holes . . .
In some of these cases, it would be possible for a good player using another type of club, the category of "lofted" fairway "Woods" (4 to 7 wood), to play a ball that is both long and high. However, in practice, the majority of golfers dread using these "fairway Woods", which are trickier to play than the Irons in many situations, and above all more difficult to play with precision (greater risks of lateral spread).